Degradation of RDX by Various Advanced Oxidation Processes: Ii. Organic by-Products

Bose, Purnendu; Glaze, William H.; Maddox, D.Scott

doi:10.1016/s0043-1354(97)00308-4

Cited by 35 publications

(31 citation statements)

References 7 publications

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“…Such a process would produce an unstable radical anion, RDX ⅐Ϫ (compound I), whose denitration could produce the unstable radical RDX (compound II). Subsequent reaction of compound II via abstraction would give the amine (compound III), or subsequent reaction of compound II via elimination of an H atom would give the monounsaturated intermediate (compound IV) (6,17,24). Methylenedinitramine is one of the expected products of decomposition of compound III or IV.…”

Section: Resultsmentioning

confidence: 99%

Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine and Its Mononitroso Derivative Hexahydro-1-Nitroso-3,5-Dinitro-1,3,5-Triazine by Klebsiella pneumoniae Strain SCZ-1 Isolated from an Anaerobic Sludge

Zhao

Halasz

Paquet

et al. 2002

Appl Environ Microbiol

102

103

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In previous work, we found that an anaerobic sludge efficiently degraded hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), but the role of isolates in the degradation process was unknown. Recently, we isolated a facultatively anaerobic bacterium, identified as Klebsiella pneumoniae strain SCZ-1, using MIDI and the 16S rRNA method from this sludge and employed it to degrade RDX. Strain SCZ-1 degraded RDX to formaldehyde (HCHO), methanol (CH 3 OH) (12% of total C), carbon dioxide (CO 2 ) (72% of total C), and nitrous oxide (N 2 O) (60% of total N) through intermediary formation of methylenedinitramine (O 2 NNHCH 2 NHNO 2 ). Likewise, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) was degraded to HCHO, CH 3 ). These findings suggested the possible involvement of a common initial reaction, possibly denitration, followed by ring cleavage and decomposition in water. The trace amounts of MNX detected during RDX degradation and the trace amounts of hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine detected during MNX degradation suggested that another minor degradation pathway was also present that reduced ONO 2 groups to the corresponding ONO groups.Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a widely used explosive that severely contaminates soil and groundwater (13,22). RDX has been found to be toxic in various terrestrial and aquatic environments (26,29). The toxicity of cyclic nitramines means that contaminated soil and groundwater must be remediated, preferably by bioremediation. Biodegradation of RDX with anaerobic sludge was extensively studied by McCormick et al. (21) and Kaplan (19), who proposed a pathway based on the sequential reduction of RDX to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX). It was proposed that the nitroso compounds undergo further transformation to hydroxylamino derivatives (HOHN-RDX), which are subsequently cleaved to produce formaldehyde (HCHO), methanol (CH 3 OH), hydrazine (NH 2 NH 2 ), and dimethyl hydrazine [(H 3 C) 2 NNH 2 ].Other research groups have employed mixed anaerobic microbial cultures that have included methanogens (1, 2), acetogens (4), nitrate reducers (12), and individual isolates such as isolates of Desulfovibrio sp. and Serratia marcescens (31) to biotransform RDX, but in most cases no clear details concerning ring cleavage products or mineralization were provided in the descriptions. Subsequent work in our laboratory (14,15,16) showed that RDX could be degraded in anaerobic sludge via intermediary formation of methylenedinitramine (O 2 NNHCH 2 NHNO 2 ), which decomposes in water to nitrous oxide (N 2 O) and HCHO. Recently, Oh et al. (23) confirmed the formation of O 2 NNHCH 2 NHNO 2 during RDX degradation with anaerobic sludge. Despite these previous efforts, there is still insufficient information regarding the roles of individual anaerobic isolates and their products during RDX degradation. Without these details, particularly details concerning...

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Section: Resultsmentioning

confidence: 99%

Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine and Its Mononitroso Derivative Hexahydro-1-Nitroso-3,5-Dinitro-1,3,5-Triazine by Klebsiella pneumoniae Strain SCZ-1 Isolated from an Anaerobic Sludge

Zhao

Halasz

Paquet

et al. 2002

Appl Environ Microbiol

102

103

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“…A Finnigan (San Jose, CA) GCQ gas chromatograph-mass spectrometer with a CTC A200S autosampler was used. 15 Ion Chromatography (IC). An ion chromatography system with a Gilson 706 pump, an Alcott 728 autosampler (50 µL), a Dionex conductivity detector, and Hewlett-Packard Chemstation software was used.…”

Section: Methodsmentioning

confidence: 99%

“…A 400 µL aliquot of15 N-ring-labeled RDX solution (in acetonitrile) was added to 1.6 mL of DI water (900 µM initial RDX) in a far-UV cell. The cell received 3900 µmol/ m 2 /s of photon flux, and the solution temperature within the cells was 38°C 15. N-labeled nitrous oxide ( 15 N 14 NO) was measured by GC/MS.…”

mentioning

confidence: 99%

Phytophotolysis of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in Leaves of Reed Canary Grass

Just

Schnoor

2003

Environ. Sci. Technol.

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Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was degraded in reed canary grass leaves exposed to simulated sunlight to primary products nitrous oxide and 4-nitro-2,4-diazabutanal. This is the first time that 4-nitro-2,4-diazabutanal, a potentially toxic degradate, has been measured in plant tissues following phytotransformation of RDX. These compounds, along with nitrite and formaldehyde, were also detected in aqueous RDX systems exposed to the same simulated sunlight. Results showed that the initial products of RDX photodegradation in translucent plant tissues were similar to products formed from aqueous photolysis of RDX. Combustion analysis of leaves following 14C-RDX uptake and subsequent light exposure revealed the presence of tissue-bound material that could not be extracted with acetonitrile. No detectable formaldehyde was emitted from the leaves. The detection of similar RDX degradation products in both aqueous and plant-based systems suggests that RDX may be initially transformed by similar mechanisms in both systems. Direct photolysis of RDX via ultraviolet irradiation passing into the leaves is hypothesized to be responsible for the observed transformations. In addition, membrane-bound "trap chlorophyll" in the chloroplasts may shuttle electrons to RDX as an indirect photolysis transformation mechanism. Results from this study indicate that reed canary grass facilitates photochemical degradation of RDX, and this mechanism should be considered along with more established phytoremediation processes when assessing the fate of contaminants in plant tissues. Plant-mediated phototransformation of xenobiotic compounds is a process that may be termed "phytophotolysis".

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“…Both III and IV can act as precursors to 4-NDAB. In the case of the polycyclic nitramine 2, 4,6,8,10,4,6,8,10,, denitration (two NO 2 -) also led to the formation of HCOOH, NH 3 , and N 2 O, but neither HCHO nor 4-NDAB were detected. The results provide strong evidence that initial denitration of cyclic nitramines in water is sufficient to cause ring cleavage followed by spontaneous decomposition to form the final products.…”

mentioning

confidence: 97%

Alkaline Hydrolysis of the Cyclic Nitramine Explosives RDX, HMX, and CL-20: New Insights into Degradation Pathways Obtained by the Observation of Novel Intermediates

Balakrishnan

Halasz

Hawari

2003

Environ. Sci. Technol.

171

192

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Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, I) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) hydrolyze at pH > 10 to form end products including NO2-, HCHO, HCOOH, NH3, and N2O, but little information is available on intermediates, apart from the tentatively identified pentahydro-3,5-dinitro-1,3,5-triazacyclohex-1-ene (II). Despite suggestions that RDX and HMX contaminated groundwater could be economically treated via alkaline hydrolysis, the optimization of such a process requires more detailed knowledge of intermediates and degradation pathways. In this study, we hydrolyzed the monocyclic nitramines RDX, MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine), and HMX in aqueous solution (pH 10-12.3) and found that nitramine removal was accompanied by formation of 1 molar equiv of nitrite and the accumulation of the key ring cleavage product 4-nitro-2,4-diazabutanal (4-NDAB, O2NNHCH2NHCHO). Most of the remaining C and N content of RDX, MNX, and HMX was found in HCHO, N2O, HCOOH, and NH3. Consequently, we selected RDX as a model compound and hydrolyzed it in aqueous acetonitrile solutions (pH 12.3) in the presence and absence of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to explore other early intermediates in more detail. We observed a transient LC-MS peak with a [M-H] at 192 Da that was tentatively identified as 4,6-dinitro-2,4,6-triaza-hexanal (O2NNHCH2NNO2CH2NHCHO, III) considered as the hydrolyzed product of II. In addition, we detected another novel intermediate with a [M-H] at 148 Da that was tentatively identified as a hydrolyzed product of III, namely, 5-hydroxy-4-nitro-2,4-diaza-pentanal (HOCH2NNO2CH2NHCHO, IV). Both III and IV can act as precursors to 4-NDAB. In the case of the polycyclic nitramine 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), denitration (two NO2-) also led to the formation of HCOOH, NH3, and N2O, but neither HCHO nor 4-NDAB were detected. The results provide strong evidence that initial denitration of cyclic nitramines in water is sufficient to cause ring cleavage followed by spontaneous decomposition to form the final products.

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Degradation of RDX by Various Advanced Oxidation Processes: Ii. Organic by-Products

Cited by 35 publications

References 7 publications

Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine and Its Mononitroso Derivative Hexahydro-1-Nitroso-3,5-Dinitro-1,3,5-Triazine by Klebsiella pneumoniae Strain SCZ-1 Isolated from an Anaerobic Sludge

Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine and Its Mononitroso Derivative Hexahydro-1-Nitroso-3,5-Dinitro-1,3,5-Triazine by Klebsiella pneumoniae Strain SCZ-1 Isolated from an Anaerobic Sludge

Phytophotolysis of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in Leaves of Reed Canary Grass

Alkaline Hydrolysis of the Cyclic Nitramine Explosives RDX, HMX, and CL-20: New Insights into Degradation Pathways Obtained by the Observation of Novel Intermediates

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